Method of paraffin deposition control



United States Patent METHOD or PARAFFIN DEPOSITION CONTROL Paul M. Barnes, St. Charles, Mo., Olen L. Riggs, Ponca No Drawing. Filed July 15, 1958, Ser. No. 748,602

6 Claims. (Cl. 252-83) This invention relates to a process for the prevention and removal of deposits of paraffin, asphalt and similar materials which accumulate in flow obstructing quantities in crude oil pipe lines and producing or standing wells.

The production of most oil wells is substantially decreased, and at times even completely halted, by deposition, on the inner surfaces of well tubing, on screens, in pumps, and in other equipment through which crude oil may be flowing, of paraflin, asphalt and other similar materials which are present in the crude. Pipe lines for the transportation of crude oil also suffer from deposition of such materials on the inner surfaces of the pipe. A crude oil pipe line having an inside diameter of 8 inches may decrease in elfective inside diameter to inches or less within as little as six months time, when a crude oil such as East Texas crude, which has a high content of paraflin and asphalt, fiows through the pipe line. Crude oils from other sources present the same problem, though the loss of capacity may be greater or less, depending on their parafiin and asphaltic content.

The removal of such deposits has been accomplished by various methods, most of which are well known in the art. Such methods include treatment of the clogged equipment with hot oil, paraffin solvents and scrapers. Each of these methods is more or less satisfactory for the removal of deposits from petroleum producing or transporting equipment, but each is expensive and usually requires that the well or pipe line be taken out of operation during the time of treatment.

The obvious answer to this problem of the petroleum industry is to utilize an effective preventive method to obviate deposition of parafiin and asphalt, without shutting down the well or pipe line. One fairly effective method of preventing these deposits in pipe lines is to maintain the temperature of the crude oil above the melting point for the parafiin and asphalt by placing heaters at intervals along the pipe lines. This solution of the problem is not satisfactory because it is not only unduly expensive, but also because it does not entirely prevent accumulation of deposits.

It is therefore an object of this invention to provide a method for preventing and removing accumulations of paraflin, asphalts, and other similar materials in oil wells and pipe lines that are producing or transporting crude oil, without the necessity of shutting down the wells or lines.

It is another object of this invention to provide an efficient and economical method of preventing and removing accumulations of parafiin, asphalts, and other similar materials in oil wells and pipe lines that are producing or transporting crude oil, which does not require the use of heaters or other mechanical or electrical equipment.

A further object of this invention is to provide such a method which may be performed without the necessity of skilled workers in the field.

These and other objects and advantages of the invention will become apparent as the invention is hereinafter more thoroughly discussed.

Broadly speaking, the present invention comprises a method for the elimination of deposition of paraflin, asphalts, and other similar materials from crude oil onto the surfaces of pipe, well tubing, pumps, screens, and other equipment through which the crude oil may flow, which consists of introducing into the crude oil an oil-soluble dispersing agent selected from a certain group of acylated hydroxy compounds.

While we do not wish to be bound by any particular theory regarding the principles by which the deposition of paraffin is eliminated by the dispersing agent of our invention, we believe that the dispersing agent coats the particles of paratfin so that the particles repel each other, thus preventing deposition. We also believe the dispersing agent removes paratiin deposits by entering the spaces between the paraffin particles and coating them, whereby the particles are repelled from each other and remain dispersed in the crude oil.

The dispersing agents of our invention, which are soluble in oil and in organic solvents, have a molecular weight range between and 550. These dispersants are certain of the acylated hydroxy compounds and are selected from the group consisting of acetyl tributyl citrate, stearoyl ethyl glycolate, and lauroyl amyl lactate.

The amount of parafiin dispersing agent that is preferred to be used in the process of our invention is from about 50 to parts per million parts of crude oil. As little as 10 ppm. or as much as 1000 ppm. of the parafiin dispersing agent may be used; however, the upper limit of the amount to be used is determined by economic factors.

The parafiin dispersing agent may be introduced into the crude oil containing paraffin, asphalt, or similar materials in any manner which is commonly employed when agents, such as organic solvents, acids, or solutions of detergents are introduced into the well bore, oil bearing formation, or oil handling equipment. Thus, the dispersing agent may be introduced alone, or as a dispersion in water, or as a solution in oil or in an organic fluid such as benzene, toluene, kerosene, carbon tetrachloride, cyclohexane, methanol, and ethanol.

A preferable process of this invention comprises the intermittent introduction of the parafiin dispersing agent into the crude oil containing system. In this embodiment of our invention, production of oil is continued until the increase in pressure in the system indicates that the deposition of parafiin and similar materials has reached a certain extent, then the paraffin dispersing agent in water, or preferably dissolved in an organic solvent, is introduced into the system. When the pressure of the system has dropped to the desired level, introduction of dispersing agent is discontinued until the presence of deposited paraifins and like materials is indicated by the change in system pressure.

We prefer this method of intermittent introduction of the paraffin dispersing agent into the crude oil containing system over the method of continually introducing the dispersing agent into the crude oil, mainly because of the lower cost of intermittent introduction.

In order to disclose the nature of the present invention more clearly, the following illustrative examples will be given. It is to be understood, however, that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims. Parts given are parts by weight.

Example 1 In order to test the effectiveness of various materials for controlling paraffin deposition, an apparatus which simulated field conditions was used. This apparatus 3 consisted of a metal reservoir having a capacity of four gallons that was maintained at 150 F. by means of an electric mantel. The fluid within the reservoir was withdrawn from its bottom, circulated through 14 feet of %-inch pipe, and returned to its upper portion. The pipe was immersed in a water bath maintained at 76 F. The exent of material deposition that took place in the cooled pipe was measured by means of a recording gauge which indicated the pressure required to maintain the flow of materials through the pipe at the rate of 300 mL/min. The reservoir was charged with a synthetic paraffin containing crude oil composed of kerosene with 3 to percent by weight of a dairy wax or a natural petroleum wax. Without added parafiin dispersing agent, the pressure required to maintain the flow of fluid through the pipe increased gradually to about 30 p.s.i. during 70 hours. When 50 p.p.m. of acetyl tributyl citrate (p.75 g.) in 20 parts of water was added to the reservoir, the pressure dropped to p.s.i. and from 1 hour to 70 hours after the addition, remained constant at p.s.i.

Example 2 The above experiment was repeated with the exception that 50 p.p.m. of stearoyl ethyl glycolate was used in place of acetyl tributyl citrate. On the addition of this paraflin dispersing agent, the pressure dropped to 10 p.s.i. and rose to 12 p.s.i. in 1 hour and remained at this pressure for 70 hours.

Example 3 Eflectiveness of use of lauroyl amyl lactate was similarly demonstrated by following the above-described procedure. On addition of 50 p.p.m. of this compound, system pressure dropped to 10 p.s.i. and remained at this pressure for 70 hours after its addition.

Example 4 When experiments were performed using 100 p.p.m., 200 p.p.m., and 500 p.p.m. of the acetyl tributyl citrate, stearoyl ethyl glycolate and lauroyl amyl lactate, the pressure developed by the system decreased with increase in the amount of dispersing agent. For amounts of dispersing agent above about 500 p.p.m., however, no appreciable change in pressure was noted.

Although it was anticipated that non-ionic detergents such as Tween 40, which is a polyoxyalkylene ether of partial palmitic acid ester, would have similar efl ectiveness in eliminating deposition of paraffin in crude oil systems, experimental results illustrated that such compounds do not have the efiectiveness of the above disclosed compounds. Tween 40, when added to the system described, completely failed to decrease the system pressure. Gauge pressures after addition of this material remained at 30 p.s.i.

Since many crude oils contain as high as 50 percent parafiin wax and asphalts, experiments were performed using a system as described for the preceding experiments but charging the reservoir with a synthetic oil containing larger quantities of dissolved parafiin wax. The same beneficial effect of the paraifin dispersing agents of this invention was noted.

This application is a continuation-in-part of our application, Serial No. 619,409, filed on October 31, 1956, now abandoned.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated to cover by the appended claims any such modifications as fall within the true spirit and scope of the invention.

We claim:

1. A process of controlling deposition of paraflin and the like from crude oil in oil producing and transporting equipment, comprising incorporating in the oil a dispersing agent consisting essentially of from about 10 to 1000 parts of an acylated hydroxy compound selected from the group consisting of acetyl tributyl citrate, stearoyl ethyl glycolate, and lauroyl amyl lactate, per million parts of the oil.

2. A process as defined in claim 1 characterized further in that said dispersing agent is dissolved in an organic solvent and then incorporated in the oil in solution.

3. A process as defined in claim 1 characterized further in that said dispersing agent is first dispersed in water and then the dispersion is incorporated in the oil.

4. A process as defined in claim 1 characterized further in that said dispersing agent is acetyl tributyl citrate.

5. A process as defined in claim 1 characterized further in that said dispersing agent is stearoyl ethyl glycolate.

6. A process as defined in claim 1 characterized further in that said dispersing agent is lauroyl amyl lactate.

References Cited in the file of this patent UNITED STATES PATENTS 2,025,984 Harris Dec. 31, 1935 2,151,185 Corruthers Mar. 21, 1939 2,580,765 Hall et al Jan. 1, 1952 2,590,852 Fein et al Apr. 1, 1952 2,602,778 Snyder et a1. July 8, 1952 2,836,559 Bock et a1. May 27. 1958 

1. A PROCESS OF CONTROLLING DEPOSITION OF PARAFFIN AND THE LIKE FROM CRUDE OIL IN OIL PRODUCING AND TRANSPORTING EQUIPMENT, COMPRISING INCORPORATING IN THE OIL A DISPERSING AGENT CONSISTING ESSENTIALLY OF FROM ABOUT 10 TO 1000 PARTS OF AN ACYLATED HYDROXY COMPOUND SELECTED FROM THE GROUP CONSISTING OF ACETYL TRIBUTYL CITRATE, STEAROYL ETHYL GLYCOLATE, AND LAUROYL AMYL LACTATE, PER MILLION PARTS OF THE OIL. 